During the coming year we intend to examine the nature of the interacton of Mn(II) with bovine factor IX, and to examine the ability of Mn(II) to substitute for Ca(II) in the activation of factor IX by Russel's Viper Venom, as well as factor XIa. Additionally, we will examine various synthetic phospholipids for their efficacy in the activation of factor X, in a system consisting of factor X-Ca(II)-factor IXa-factor VIII-lipid.